Microtechnologies for Power management

Transcription

Microtechnologies for Power Management
Prof. Christian Piguet, Jean-Félix Perotto
CSEM, Neuchâtel. Switzerland
CrossRoad
Outline of the Presentation
• Introduction to Energy Sources
• Review of some well-known as well as new Energy Sources
• Human Energy Sources
• Power Management
• Perspectives and Conclusion
A very good reference used in this presentation:
Thad E. Starner, Joe Paradiso, « Human-generated Power for Mobile Electronics »
In « Low-Power Electronics Design, edited by C. Piguet, CRC Press, 2005
MicroPower | C. Piguet | Page 2
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Technology Pace
• Battery Capacity:
• Factor 3!
• The last one!
• Hard Disk:
• First one!
• Factor 4’000!
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Well-known Sources of Energy
• Many Various Sources of Energy:
• Battery Cells, 300 mWh/cm3 for Lithium cells, peak current, idles
modes and power management, pulsed discharge in case of
several batteries, battery models
• Miniature Fuel Cells, 0.1 to 25 watts, several mA consumed
continuously
• Solar Cells, 100 µA/cm2
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New (?) Sources of Energy
• Fuel burning generators that produce heat converted in electricity by
thermocouples
• Energy from vibrations in noisy environment (ships, trains, industrial)
• Micro Power Generators using Nickel-63 Radio-isotope
• Thermoelectric, 2-10 µW, wristwatches with 1’000 Peltier elements, now
MEMS such as silicon-based thermo generator
• Human powered sources, walking shoes that produce energy by piezo
effect, automatic mechanical watches (0.5 µW), microturbines, arm
movements, vibrations with 10µW/cm3 to 50-500µW/cm3
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Evolution of Batteries
• Slow improvement
• Certainly not on Moore’s Law!
IEEE Proceedings, 1995
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Development of Li-ion Battery Cells
Highest energy
density of today’s
rechargeable
batteries
18650 Li-ion Cell Energy Density
Energy Density (Wh/L)
600
500
400
Energy
300
200
Rechargeable Battery
Capabilities: Naturally
Plateau as Systems
Develop
Extrapolated, Nomura Inst.
100
0
1995 1997 1999 2001 2003 2005 2007 2009
No Moore’s Law
Doubling on a Regular
Basis
Year
Marc Doyle, DuPont
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Need Higher Energy Density
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Fuel cells: Renewable Energy Source
• Membrane splits
electrons off hydrogen
Breathe Air
Fuel Inlet
• Electrons recombine
with proton on other
side in catalyzed
reaction w. oxygen to
form water
Waste
• …After they are routed
through external circuit
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Fuel cells for Mobile Platforms
• Superior to batteries at 100 Watt-hr
(Metal hydride)
• Fuel cell technology improves at
approx. 10 watt-hr/yr
• Parity with laptop batteries in 5 Years
• Cell phones (2-5 Watt-hr) soon to
follow (another 4-5 years)
• Direct Methanol
Motorola Mobile Charger:
2” x 4” x 0.5” (10/01)
Belt holder
1 month of calls per charge
2-4 years
200 million units by 2010
Other players:
NEC,
Mechanical Technology,
Manhattan Scientifics
Fraunhofer Institute
• Battery-FC hybrid (FC at 1 Watt
charges battery)
• Power phones for over a month?
• Replacable cartridge to feed fuel,
collect water...
Photo showing conceptual Motorola/LANL fuel-cell-phone
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Solar Photovoltaic
Limited Efficiencies:
Franhofer ISE
Freiberg
1 Watt under
halogen
20% eff.
Amorphous Silicon
13%
Crystalline Silicon
22%
III-V devices, concentrators, etc.
30%
• DOE goal to get amorphous Si cells to 15%
• 0.0021 W/cm2 at moderate latitudes
• Multiple junction devices, GaAs, concentrators get 30-34%
• Still in Lab
• In most places, not readily suitable for mobile devices
• Need the sunlight, Need the area…
• Possible for some low-power embedded sensor packs
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MIT Micro Gas Turbine Generator
112 inch
Microturbine with electric-field induction generator
0.5 inch
Power Output
Weight
Specific Energy
Micro Turbo
Generator
50 W
50 grams
3500 W-hr/kg
LiSO2 Battery
(BA5590)
50 W
1000 grams
175 W-hr/kg
• A portable power source with ten-fifty times the power density of state-of-art
batteries
• …In the size of a shirt button...
Marty Schmidt and collaborators, MIT Microsystems Technology Laboratory (MTL)
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MIT Micro-Engine
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MIT: Six-Wafer Microcombustor
• 2.4 MRPM (1.2 now; geometry/precision)
• Rotor breaks the sound barrier
• Rotor supported on laminar air bearings
• Silicon carbide parts where higher temperature
• Combustion in Silicon
• And, of course, making generator work!
15 masks, 12 deep etches
through 3.8mm, 5 aligned wafer
bonds
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Energy from the Environment
• Vibration/acoustic/turbulence
• MEMs devices
• Piezoelectric pickups
LC Tag
• Places where loud noise and strong vibration
present
– Ships, machinery, underwater
• Thermal
• Need large surface area, big Diff Temperature
• Ambient electromagnetic
• AM radio
• Need big dipole…
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Microstructures for Vibrational Energy Recovery
Piezo: AlN or PZT : a mass is
suspended at the end of a cantilever
• MEMs Electrostatic Force Arrays
• Work like condensor microphone
• Voltage across plates creates current as they deflect
• Need battery or other bootstrap
MCNC, Chappel Hill
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Capacitive MEMs Driven Condenser Power Supply
The energy is transduced
through the use of a variable
capacitor which has been
designed with MEMS
technology.
• MEMs motor in reverse…
• Special power-control electronics designed & fabbed
• MEMs now under fab
• Expect 8 uW
• Could tile for more power
• Will provide power for their sub mW “picoJoule DSP”
• Embedded low-power sensing applications
– Vibrating bulkheads (ships), mechanics, etc.
Anantha Chandrakasan, Jeff Lang - MIT MTL
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Electrostatic Capacitive Vibration to Electricity
S. Roundi, P. K. Wright, IMECE 2002
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Vibration-Based Magnetic Power Generation
Electromagnetic:
- difficult to scale
- low output voltages
About 100 µW
4*4*10 cm
180 mV
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Micropower Generator using Nickel-63 Radio-isotope
Cantilever is bending by
the tip trapping nuclear
charges, resulting in
electrostatic force.
This mechanical force is
transformed in electricity
by piezo PZT (Plomb
Zirconate Titanate)
Continuous 10 to 20 nW
Pulsed 30 to 40 µW
R. Duggirala, H. Li, A. Lai, Cornell Univ. Ithaca, US, ISSCC 2006, 23.1
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Human Energy Sources
• A lot of Energy from
the human body
• Body Heat
• Breathing
• Finger Motion
• Blood Pressure
• Arm Motion
• Walking
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Energy consumed by a person with various activities
Activities
To sleep
To be in a bed
To be seated on a chair
To be standing
To chat
To eat a lunch
To drive a car
To play music
To clean up a house
To run at 5 km/h
To swim
Mountain Climbing
To run on a long distance
To run a sprint
Kilocalorie/hour
70
80
100
110
110
110
140
140
150
350
500
600
900
1400
Watts
81
93
116
128
128
128
163
163
175
407
582
698
1048
1630
So it seems it should be possible to scavenge some watts from this!!
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Thermoelectric Generators
• Very well known principle: many Peltier cells in series
• However, a brace around the neck produces only 0.2 to 0.32 watts.
• It has been used in electronic wristwatches (proposed in 1978, US patent
4'106’279 by Martin and Piguet)
• Some microwatts
• Seiko “Thermic”
• Today: new materials
104 elements (80 µm thick and 600 µm long) are attached to 2 mm x 2 mm boards connected in
series. 10 connecting units form the thermoelectric generator mounted in SEIKO THERMIC®.
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Seiko SII Thermal Energy Watch
1.7mm
Thermoelectric unit
2.14mm
1.27mm
2.14mm
2.36mm
Thermoelectric module
Thermal energy watch
Watch
movement
Heat flow
• Uses 10 Thermoelectric modules and a
booster IC
• Runs off body heat
• Low DT, limited surface area, low efficiency ->
Microwatts...
Battery
Booster IC
arm
Adiabatic case
Thermoelectric (Photo)
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The ETA Autoquartz Self-Winding Electronic Watch
The Swatch Group (SMH)
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The ETA Autoquartz Mechanism
• Proof Mass winds
spring which pulses
generator
• Generator always run at
optimum rate (10-15K
RPM)
• Power stored on spring
until threshold is
exceeded
• Generator pulsed for 50
msec
• Yields 6 mA at >16
Volts
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Seiko AGS System
Oscillating weight
Oscillating
weight
Charge control
circuit
Oscillating
weight gear
Secondary
power supply
Gear train
Transmission gear
Drive circuit
Rotor
Stator
Coil
Stator
KINETIC outline
diagram
• Proof mass oscillation directly cranks generator rotor
Rotor
Coil
Oblique view
• Little intervening mechanics
• Charge accumulated on capacitor
• Power Output:
• 5 µW average when the watch is worn
• 1 mW or more when the watch is forcibly shaken
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Seiko Experimental AGS for Marine Mammals
• Uses watch AGS
(Automatic Generating
System) components
• Power Output is 5 to 10
mW
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Breathing and Blood Pressure
• A mask applied on the face, containing a turbine, 0.4 watt
• A belt on the body, with 2 to 5 cm of change in chest circumference, also 0.4
watt
• Blood pressure, some microwatts, but to locate a microturbine into the body
would increase the heart load, it could be dangerous!. Applications could be
self-powered medical sensors.
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Modern Magnetic Generators Products
• 60 turns (1 min)
stores 0.6 Watt-hr
• 40% efficient
• Today’s laptop supply
roughly 50 W-hr
• Freeplay/Motorola
windup cellphone
charger (30 sec = 6 min
for $49.)
Step!
Shake!
Crank!
Squeeze!
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Power Harvesting Shoes
Piezo
PVDF Stave
Molded into sole
Energy from bend
Ppeak @ 10 mW
<P> @ 1 mW
Flex PZT Unimorph
Under insole
Pressed by heel
Ppeak @ 50 mW
<P> @ 10 mW
Responsive Environments Group, MIT Media Lab, 1998 IEEE Wearable Computing Conference
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Rotary Magnetic Generator
• Attaches lever-driven flywheel/generator to shoe
- 3 cm deflection, bulky
- Suboptimal (e.g., better integration, hydraulics...)
• Produces a quarter watt average (@ 1 W peak), but very obtrusive!
Responsive Environments Group - MIT Media Lab
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Electric Shoe Company
• Piezoelectric “crystal” struck
with each footfall
• Claims to generate 100-150
mW
• Used in walk across Namibian
Desert, summer 2000
• Cellphone battery partially
(e.g., half) charged after 5 days
of walking
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The self-powered wireless switch
• Wireless input device powered by its own activation
• No need for power or signal wiring, batteries, etc.
• Just “drop” into homes, offices, public spaces, vehicles…
• A QWERTY typist, about 7 to 10 mW
Zenith
‘Space
Command”
Crisan, A. (Compaq), Typing Power,
US Patent No. 5,911,529, June 15, 1999
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How to generate supply voltages for SoCs
• Very diverse energy sources
• Voltages and currents provided can be very small or quite large
• Voltages to be generated for supplying various chips:
• Small voltages (0.6 to 0.9 Volt) or large (3.0 Volt for external EEPROM)
• Could be both, so smaller AND larger voltages than the energy source
• Currents could be small (microcontroller) or large (PA in TX radio)
• Sub-blocks can work continuously or by bursts
• DC-DC converters for micropower
• DVS: Dynamic Voltage Scaling depending on running, sleeping modes
• From batteries, but more and more from energy scavenging
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Supply Voltage Evolution (I)
portables devices
1.5
1.2
Vdd (V) 0.9
0.6
0.5
0.3
0
1999
2002
2005
2008
2011
2014
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Supply Voltage Evolution (I)
Low Voltage Energy Sources are more and more interesting
alcaline batteries
1.5
1.2
Vdd (V) 0.9
Miniature fuel cells
0.6
0.5
0.3
0
Thermogenerators
1999
2002
2005
2008
2011
2014
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Dissipated Power Evolution
Energy Sources providing low energy are more and more interesting
Power related to same computation performances
1
P = FCU 2
F = cte
C ∝ Lgate
Prel 0.1
leakage
?
0.01
1999
2002
2005
2008
2011
2014
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Capacitive DC-DC Converters
♦ Conversion factors are fixed by the circuit topology and are of the form M/N.
♦ Complexity of the circuit and the number of capacitors is dependent on M
and N, roughly max (M,N).
♦ To fine adjust the output voltage requires a dissipative regulator.
♦ Capacitors can be integrated on chip until 50 pF (with maximum currents of
about 50 µA), above external capacitors are required.
Regul
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Adiabatic DC-DC Converters
VADIABATIC
 Adaptive dc-dc capacitive down
converter generates a voltage as
close as possible to the optimal
supply voltage.
Battery voltage reduction factor
1
1.0
2/3
1/2
 This reduces the dissipative
part of the regulation and
increases the battery lifetime.
VOUT
0.6
0.5
0
0
0.5
0.9 1.0 1.1
1.4
1.5V
VBAT
 Global efficiency of 80 % is
obtained and 40 % battery lifetime
improved at least.
Adiabatically reduced battery voltage during the
battery discharge.
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Regulation of capacitive DC-DC converters
Usource
Usource
ref
Usource
Usource
Ured
Uload
Adiabatic
Reduction
i.e. 1/2
ref
Ured
+
-
dissipative
Uload
Ureg
Uload
+
-
Ureg
dissipative
Adiabatic
Reduction
i.e. 1/2
Uload
load
Post-regulation
load
Pre-regulation
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DC-DC for both 0.6 Volt (IC) and 3.0 Volt (EEPROM)
Below: Example for a hearing aid device
alim control
switch control
5 MHz
switch matrix
reg
reg
0.6V
3.0V
C1
C2
0.9 mm
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CSEM Design Examples
• Several power management blocks have been designed:
• Capacitive DC-DC up & down converter in TSMC 0.13µm process
• Generation of two voltages 0.6V & 3.0V from the 1.5V battery with
85% efficiency
• 2mA load current; -40dB PSSR; 25 µA power consumption in
stand-by
• Capacitive DC-DC up converters in TSMC 0.18µm process
• Two 2.4V supply voltages generated from the 1-1.8V battery with
80% efficiency
• One with 2+1 external capacitors; 10mA load current
• One with 2 integrated capacitors + 1 external; 5µA load current
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Inductive DC-DC Converters
♦ Conversion Factor is given by switching duty cycle.
♦ Circuit topology and complexity as well as the number of components are
fixed and independent of the conversion factor,
♦ To fine adjust the output voltage DOES NOT require a dissipative regulator.
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DC-DC Inductive Buck Down Converter
IL
IL
L
UB
Uout
Phase I
Source provides a current IL to
the inductance et to the load
U out = U B D
IL
UB
IL
L
Uout
Phase II
By inertial effect, the inductance
continues to provide a current IL
to the load with a voltage
smaller than UB.
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DC-DC Inductive Buck Up Converter
IC
L
Uout
IL
IL
UB
Phase I
Source provides a current IL to
the inductance et to the load
U out = U B
IL
Uout
L
IL
UB
1
D
Phase II
By inertial effect, the inductance
continues to provide a current IL
to the load with a voltage larger
than UB.
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CSEM Design Examples
• Inductive DC-DC down Buck converter in TSMC 0.18µm process
• 1.2V supply voltage generated from 3V
• 10mA load current; -42dB PSSR
• Development of a power management circuit for 2.4 GHz transceiver
•
Buck/Boost Converter 10 mW
• Development of inductive DC-DC converters in sliding mode
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DVS: Dynamic Voltage Scaling for INTEL X-Scale
• The INTEL X-Scale processor is the old DEC StrongARM-2
• Frequency and voltage can be modified continuously. It has four modes:
• Running
• Idle in which the clock is stopped
• Stand-by in which the PLL is stopped and source-to-bulk back biasing is
applied to minimize the leakage current
• Sleep in which everything is stopped and memories loose their data (Vdd
reduced)
Frequency
50 MHz
400 MHz
600 MHz
800 MHz
Drystone 2.1 MIPS
62
500
750
1000
power
10 mW
180 mW
450 mW
900 mW
Voltage
0.75 V.
1.0 V.
1.3 V.
1.65 V.
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DVS for StrongArm
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Trends for Energy Sources
• It is extremely difficult to design new energy sources for devices like laptop
computers, PDAs and self phones
• There are also some issues about security, i.e. methanol cartridges will
probably not be authorized in planes
• For microwatts applications, it is more easy to find vibrational, thermoelectric
or solar or other energy sources depending on the applications.
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Trends for SoCs Power Consumption
• Power Consumption of SoCs has today two parts:
• Dynamic power
• Static power
• Static power is increasing very rapidly compared to dynamic power in very
deep submicron technologies
• Total power is not predicted to be smaller as consumers require always new
functions (that are more and more unused!!)
• It is questionable if consumers will require “low cost” devices (as low cost
cars such LOGAN by Renault) for self phones or laptops. In that case, total
power could be reduced.
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Conclusion
• Extreme diversity in energy sources
• New energy sources are available as new MEMS designs (vibrations, fuel
burning generators, thermoelectricity, piezo, human powered sources)
• Also a large diversity in specifications of SoCs, with both smaller and larger
voltages than the one provided by the energy source, a quite large range in
currents and DVS which is more and more mandatory for SoCs.
• So the design of power management circuits is difficult, as the re-use of
already designed circuits is difficult, as the specs are generally quite different
form circuit to circuit.
Thank you for your attention.

Microtechnologies for Power management

Transcription

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